1. Field of the Invention
The present invention pertains to heart valve prostheses and in particular, to bi-leaflet heart valve prostheses using pivotable valve members.
2. Description of the Prior Art
Various types of heart valve prostheses have been developed which operate hemodynamically as a result of the pumping action of the heart. Among the types of heart valves which have been developed are valves having single disk occluders which pivot along an eccentric axis to open and close the heart valves, such as that described in U.S. Pat. Nos. 4,306,319 and 4,011,601, and bi-leaflet heart valves, such as those described in U.S. Pat. Nos. 3,903,548 and 4,605,408. The above-mentioned patents have various arrangements for pivotally connecting the valve or valves to a body member. However, the need continues for improved heart valves which are intended for permanent implantation into the human heart.
In its open position, a valve should provide a passageway which is large and which has good flow characteristics so that blood flows freely therethrough with a minimum of drag and eddy currents. The heart valve should be responsive to blood flow to quickly open during the pumping stroke of the heart and snap back quickly when the heart relaxes to prevent regurgitation of the blood. The heart valve must, of course, be biocompatible and thrombo-resistant, and in this regard, it is important that all surfaces be well washed by blood to prevent stagnation which might lead to eventual clotting. The opening and closing of the valve should be sufficiently soft so that the patient is not disturbed by the sounds produced. Furthermore, the action of the valve should be such that it does not cause hemolysis (breaking of blood cells). The heart valve must withstand countless openings and closings, and particular care should be exercised so that the load-bearing surfaces, such as the pivot points and stops, do not wear out during the life of the patient. The above characteristics may be desirably achieved with a simple design which not only simplifies manufacture, but also reduces the quality control problems associated with complexity.
The interengagement structures by which valve members are mounted in heart bodies frequently represent regions where blood is most likely to clot and stagnate. Some designs of heart valves, such as those disclosed in U.S. Pat. No. 4,373,216, provide improved performance in this regard. For example, the valve mounting arrangement of U.S. Pat. No. 4,373,216 requires window-like cut-out portions at the valve lateral edges to provide clearance for guide members protruding from an inner wall of the valve body. Generally, it is desirable, if at all possible, to provide valve bodies having an internal bore of maximal size, and to provide valves fitting therein having smooth continuous edges free of windows, cutouts and the like.